Switching arrangement for compensating voltage variations



p 1933- H. v. ALEXANDERSSON 1,928,523

SWITCHING ARRANGEMENT FOR COMPENSATING VOLTAGE VARIATIONS Filed Sept 8, 1950 Alp Patented Ed, @333 SWITQHKNG ARRANGEMENT FOR C'OMPEN- I EATING VULTAG-E JAREA'EIQNS Harald Valdemar Alcrandersscn, Stockholm,

Sweden, assignor to Telefonaktiebolaget L. M.

Ericsson, Stockholm, Sweden, a

1 Sweden 1' company of I st ircases September 8, issasemi N 480,512, 1 i and in Sweden September 13, 1929 The p esent invention has for its object a switch g arrangement in telephone plants. lVi'ore especially, is invention relates to telephone plants having signalling relay connected be tween the central battery and the feed coils of the talking lines. v i

The invention substantially characterized in said element in nee decreases other, by way of example copper plates which the one side are coated by a layer of cuprous oxide. I

The invention may also beapn ied alternating current circuits the shunt then consisting of two parallel connected rectifiers or the like turned in opposite directions which areccnnected into circuit parallelly with a resistance in which a compensation of the voltagevariaticns is desired.

The invention will be more closely described with reference to the accompanying drawing on which Figure 1 shows an embodiment of the invention whereas Figures 2 and 3 are diagrams which will be more closely described in the following.

In Figure 1 there are shown some ofythe circuits 4,0 in a telephone plant having a signalling-"relay con nested into circuit between a central battery and the talking lines and adapted to be actuated upon calls'and to perform a switching operation coinmon to all calls. In the example shown on the drawing such a relay 1 is connected into circuit in one line branch of the talking l" e 3 extending. from the central battery 2to which line the d11- ierent talking lines are connected in known inauher over feed coils. The relay is here adapted to 50 close the circuit or" amotor 4, upon calls, which motor, by way of example, may serve to drive selectors or other mechanical devices and which normally is disconnected but is started as soon as a call occurs. When current is tapped off from the battery 2 on accountof a call, the relay 1 is it the relay, vs. is adapted to be actuatedl'Claim; (oi. 179 -16) 1 energized and closes at its contact '5 the circuit or" the motor The relay 1 must consequently be so sensitive'that it is actuated by the current generated by a single calls The relay 1 must, besides, be of such a nature'that the drop of voltage in its winding is not too high at the maximum load and preferably not exceeding 0.5 volts in order to avoid overbearing; By connecting a rectifier 6 or the like into circuit parallellyi with the l, the relay according to the invendrop of voltage in the winding upon a maximum lead may he kept at a low value.

A relay disposed according to Figure 1 may also be advantageously used for switching on and off a current source for charging the battery 2 in such cases when charging has to take place only during a conversation.

Figure 2 is a diagram in which the vertical axis is marked VR denoting voltage and resistance, while the horizontal axis is marked I denotingamperes and showing curves obtained in measurements in a circuit arrangement according to Figure 1. The measurements are made for amperages in the line 3 upto nine amperes.

The curve 7 represents the total resistance of the relay 1 and the rectifier 6 parallel connected therewith whereas the curve 8 shows the corresponding drop of voltage for said resistance. At nine amperes the drop of voltage'willbe 0.52 volts whereas said drop at 0.5 amperes amounts to 0.25 volts. The straightline 9 shows in comparison the drop of voltage-at constant resistance, from which we make the conclusion that the drop of voltage at 0.5 amperes only amounts to about 0.03 volts and thus is about 8.5 times less than L when using a rectifier shunt according to the in vention. In an arrangement according to the invention the relay will thus be considerably more sensitive at small amperages.

An arrangement according to Figure very advantageous in regard to the overhearing or cross-talk phenomena which occur in central battery systems thereby that a part of the speech currents, in spite of the feed coils, enter the battery and bring about voltage variations therein which may influence othertalking circuits. One has then to take into account those small voltage variations AV, which are generatedby a certain current variation AI, corresponding to an crosstalk resistance a 9L AI d I the amplitude of which is dependent upon the 1 is also 65 tion, he made highly sensitive at the same time slope of the curve 8 for the drop of voltage. Apparently said curve to its greater portion has a less angle of slope than said line 9 representing the drop of voltage for a relay having a shunt of constant resistance. The cross-talk resistance is consequently correspondingly less. The curve 10 represents the cross-talk resistance age. From this we make the conclusion that the curve has the desired appearance only at voltages of a definite direction. In circuits carrying direct current it is consequently of importance that the rectifier element is connected into circuit in the correct direction in relation to the current direction. A rectifier element of the kind in question should consequently be so connected into circuit that the current passes through the element in the direction in which the element offers the smallest resistance.

In a switching arrangement for telephone systems, a central battery, a plurality of talking lines, two conductors in each of said lines connected to opposite poles of the battery each over a feed coil, a signalling relay connected into circuit between the battery and the feeding coil, and a connecting element having electrical valve action shunted with said relay.

HARALD VALDEMAR. ALEXANDERSSON. 

